According to the study of the inventors, the following technologies have been considered to contribute to previous disk array apparatuses and the control technology for the apparatuses.
For example, when an error is caused in operation of writing or reading data into or from a disk drive in the previous disk array apparatuses and the control technology for the apparatuses, repeating operation of write or read for data, so-called retry operation is executed. In the retry operation, a reason for the caused error is cleared, the number of the retry operations corresponding to the cleared reason is set, and, when there is success in recovery from the error within the set retrying times, the success is reported as “recovered” to a host system (Refer to Japanese Patent Application Laid-open No. 2003-141824).
Recently, a larger space of a hard drive in a disk array apparatus has caused the higher density in the recording density. Thereby, even if the error rate per recording density is similar to that of the previous disk drive, the number of errors per disk drive is proportional to the recording density. Accordingly, when all recoveries by the retry operations are reported to a host system in a similar manner to that of the previous cases, the number of error reports becomes too much and there is a possibility that a related disk drive is likely to be judged as a defective one.
As one example of solutions for the possibility, when the retry operations are executed several times, not a method in which “recovered” (success in the recovery) is reported to a host system, but a method in which normal termination is reported to the host system, that is, a so-called un-reported retry is adopted in some cases. In the un-reported retry, the host system using the disk drive usually monitors the response time of the disk drive, but, considering sudden temporary failures, it is a common practice to set a monitoring period as 10 through 100 times normal response time. Therefore, a disk drive, in which the recovery operation is continuously executed to cause the response time which is 1.5 times through 2.0 times the normal value at all times, is not judged at detection to be a delayed drive.